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Cutworms

Overview

Important turf damaging cutworms include the black cutworm, Agrotis ipsilon (Hufnagel); the bronzed cutworm, Nephelodes minians (Guenee); and the variegated cutworm, Peridroma saucia (Hubner). Cutworms are found throughout North America, although the black cutworm is a pest throughout the world, and the bronzed cutworm is more prevalent in cooler climates. All species of turfgrasses may be attacked by these semi-subterranean, night-feeding pests. On golf course greens and tees, black cutworms are a perennial problem. Larvae are mostly hairless with a few scattered bristles. They have 3 pairs of true legs as well as 5 pairs of prolegs, and most will coil into a spiral when disturbed. When full grown, the larvae are 1.4 to 2.0 inches long. Adults are dull-colored moths with a wingspan of 1.4 to 1.8 inches, with the wings kept folded flat over the body at rest. Black cutworm adults are gray with black markings, bronzed cutworm adults are a mottled reddish-brown color, and the variegated cutworm adult moth may be brown or gray. Cutworms overwinter as larvae or pupae in the Northern states. In Southern turf, activity occurs all year round. Black and variegated cutworms cutworms have 2 to 4 generations per year in the north, whereas in southern geographies, they have 3 to 7 generations per year. Bronzed cutworms have only 1 generation per year throughout its range. An individual female may lay up to 2,000 eggs over a period of several days. 3 to 10 days later, the larvae hatch and feed on grass blades for 20 to 40 days.

Damage

Cutworms usually dig a burrow in the ground or thatch or may use an aeration hole as a burrow. At night they emerge to clip off grass blades and shoots. This feeding damage often appears as circular spots of dead grass or sunken spots that look like ball marks on golf greens. Bronzed cutworms are active in fall and spring and have been known to completely strip off a lawn at ground level.

Management

Because cutworms can be difficult to locate, the use of a soap flushing solution is often needed to determine population pressure. Control measures are warranted if 3 to 8 or more larvae are found per square yard of fairway or lawn turf. Finding only a few on greens or tees may indicate control measures are needed. Cutworm control is obtained when the cutworms either consume or Trials conducted in Indiana, New Hampshire, Ohio, Pennsylvania, South Carolina and West Virginia Trial conducted by Dr. Chris Williamson, University of WI, 2001 DAT = Days After Treatment contact the pesticide treated turf/grasses.

Treatment

Apply Talstar ® Professional or Talstar ® Select (RUP) Insecticide at the rate of 0.18 to 0.25 fluid ounces per 1,000 sq ft in the afternoon or evening and delay irrigation for 24 hours after application. High, dense canopies may require higher application rates, especially when the populations of cutworms contain a mixture of life stages. The maximum application rate for Talstar Professional or Talstar Select (RUP) for cutworm control is 1.0 fluid ounce per 1,000 sq ft. Larvae hatching several days after application are also controlled by the long residual activity of the product. Apply Talstar ® PL Granular Insecticide, Talstar ® Xtra Granular Insecticide at the rate of 1.15 to 2.3 pounds per 1,000 sq ft. Existing soil moisture is often sufficient to release the active ingredient from the sand-based granule, and subsequent dew or rainfall will ensure the release. However, irrigating the treated area with up to 0.1 inch of water after application of Talstar PL granular will usually result in quicker control of cutworms. This level of irrigation will release the insecticide from the granule but keep it within the feeding area of the cutworms.